Variable resistance control device



Nov. 17, 1953 A. M. DAILY ETAL 2,659,793

VARIABLE RESISTANCE CONTROL DEVICE Filed Nov. 30, 1951 2 Sheets-Sheet lNov. 17, 1953 A. M. DAILY ETAL 2,659,793

VARIABLE RESISTANCE CONTROL DEVICE Filed Nov. 30, 1951 2 Sheets-Sheet 2Arthur MJJaz/y Merv/27 flAz'zsman Patented Nov. 1'2", 1953 VARIABLERESISTANCE CONTROL DEVICE Arthur M. Daily and Mervin B. Arisman,Elkhart, Ind., assignors to Chicago Telephone Supply Corporation,Elkhart, Ind., a corporation of Indiana Application November 30, 1951,Serial No. 259,271

12 Claims.

This invention relates to electrical control devices and has moreparticular reference to dual variable resistance control devices such asthat shown and described in Patent No. 2,484,667 issued to Mervin B.Arisman et al., October 11, 1949. Variable resistance devices like theseare used in radio and particularly television receivers,

and comprise two control units connected toether in tandem with theshaft of one hollow and having the shaft of the other rotatable therein.

Previously, the rear control unit of the device was mounted upon theback of the front control unit with a separator plate of the correctthickness interposed therebetween, and the inner control shaft for therear unit was held against rearward motion thereinto by means of a C-washer engaged in an annular groove in the inner shaft ahead of thespacing plate.

One of the main objects of this invention is to effect a saving in bothmaterials and parts employed in the control device of the type referredto so as to achieve a greater degree of simplicity but withoutsacrificing ruggedness and high quality workmanship. According to thisinvention this object is achieved through the elimination of theaforementioned conventional spacing plate and G-washer formerly usedwith such control devices.

More particularly this invention has as one i of its objects theprovision of a dual or tandem resistance control device of the characterdescribed wherein the back wall of the front unit has a central portionthereof embossed axially outwardly of the plane of the back wall forengagement with the front wall of the rear control unit to hold thelatter spaced from the front unit a distance corresponding to thethickness of the spacing plate formerly used to hold the two controlunits in proper axially spaced relation. Hence, this outwardly embossedrear wall portion of the front control unit eliminates the need for theconventional spacing plate.

Also according to the present invention, the outwardly embossed centralportion on the rear wall of the front control unit has a key-hole shapedaperture therein the larger portion of which is capable 01'accommodating the inner control shaft to enable assembly of the twounits, and the smaller portion of which aperture receives an annularlygrooved portion of the-inner control shaft to lock the same to thehousing of the front control device, against rearward motion relativethereto, so as to thereby eliminate the need for the separate c-washerformerly used for this purpose.

While the inner control shaft is thus supported by the rear wall of thefront control unit against rearward end thrust on the shaft in a mosteffective manner, it is also a purpose of this invention to provide anovel thrust bearing for the front control unit by which the hollowoperating shaft thereof is supported against rearward end thrustthereon. a

While this may be accomplished in a manner similar to that shown anddescribed in the copending application of W. H. Budd, Serial No.204,401, filed January 4, 1951, now Patent No. 2,628,298, it is thepurpose of this invention to provide an improved end thrust bearing, forthe hollow control shaft, which more readily lends itself to the compactdesign of the control device of this invention.

With the above and other objects in view, which will appear as thedescription proceeds, thisinvention resides in the novel constructionand arrangement of parts substantially as hereinafter described, andmore particularly defined by the appended claims, it being understoodthat such changes in the precise embodiment of the hereinafter disclosedinvention may be made as come within the scope of the claims.

The accompanying drawings illustrate two complete examples of thephysical embodiment of the invention constructed in accordance with thebest modes so far devised for the practical application of theprinciples thereof, and in which:

Figure 1 is a side view of a dual or tandem variable resistance controldevice embodying the principles of this invention, parts thereof beingbroken away and shown in longitudinal section;

Figure 2 is an elevational view of the device shown in Figure 1, viewingthe same from the underside;

Figure 3 is a group perspective view of the control device but showingthe mechanism removed from the front control unit;

Figure 4 is a cross sectional view taken through Figure 1 along theplane of the line H;

Figure 5 is a detail sectional view taken through a portion of Figure 3along the plane of the line 5-5;

Figure 6 is a view similar to Figure 1 but illustrating a slightlymodified embodiment of the invention; and

Figure 7 is a group perspective view similar to Figure 3 showing theparts of the control device illustrated in Figure 6.

Referring now particularly to the accompany-' ing drawings, the numerals5 and 6 designate the front and rear control units of a dual or tandem 3variable resistance control device, such as that forming the subject ofthe aforesaid Patent No. 2,484,667, and designed particularly forcompactness because of its widespread use in radio and televisionreceivers.

Each of the control units comprises a housing including a cup-likehousing part 1 for the front control unit and a similar cup-like housingpart 2 for the rear control unit butsiightly smaller in diameter thanthat of the front unit. The open front of the cup-like housing part 5 isclosed by a relatively flat base ll of insulating material and a similarbase of insulating material I I closes the open front of the cup-likehousing part 8 of the roar control unit. The insulating base l0 natwiseabuts the rim ll of the housing part 1 and h nxed thereto by a number oftabs I3 projecting forwardly from the side wall of the housing partthrough peripheral notches in the base II, and bent inwardly over thefront face of the base to hold the same clamped against the rim ll. Thismanner of securing the base it to the housing part 1, of course, holdsthe base in spaced parallel relationship to the bottom wall I! of thehousing part 1, which bottom wall provides the back wall of the housingfor the front control unit.

base ii of the rear control unit 8 also flatwise abuts the rim ll of therear housing part 8. The tabs [1 of the rear housing part I, however,are longer and wider than the tabs I! previously described, and haveforwardly facing shoulders l1 thereon spaced a distance ahead of thefront side of the base H and abutting the rear wall of the front controlunit. Reduced extremities it on the tabs I1, however project forwardlythrough slit-like apertures in the wall it of the front unit and arebent over onto the inside face of this wall similarly to the tabs II, tosecure the units together with the back wall ll of the front unit spacedfrom the adiacent base of the rear unit by the shoulders l1.

Stationarily mountediupon the inner face of each of the insulating basesis an arcuate resistance strip II and a collector ring 20, and the usualterminals 2| extend from the ends of the strips and rings to be exposedat the exterior of the control device. Cooperating with the resistancestrip and collector ring of each control unit is a eontactor 22 mountedupon the front face of a contact carrier or driver 22 preferablycomprising a disc of insulating material. The driver 22 of the frontunit is fixed upon the inner end of a tubular control shaft 25 freelyrotatably journalled in a bushing 28 on the base II, the bushing alsoserving as the means for mounting the control device upon a panel (notshown) or the like. The driver 22 of the rear unit is fixed to the innerend of a solid control shaft 21 rotatable inside the tubular shaft 25and projecting axially rearwardly through the front control unit intothe interior of the rear control unit.

The construction of the control device described thus far generallyfollows that shown and described in the copending application of W. H.Budd. Serial No. 204,401 mentioned previously, with the exception thatthe cup-like housing part I of the rear control housing of thisinvention is smaller in diameter than that of the front control unit.This has the advantage of permitting the attaching tabs l1-il of therear unit to project straight forwardly from the side wall of itshousing part I for connection with the rear wall I. of the fronthousing. the tabs ll be- '4 ing spaced slightly inwardly from the sidewall of the front housing part 1.

According to this invention, the customary spacing plate whichpreviously was interposed between the back wall of the front controlunit and the insulating base of the rear control unit is eliminated,along with the customary C-washer by which the control shaft of the rearcontrol unit was supported against rearward end thrust thereon. In thepresent case the proper axial spacing between the two control units isachieved by the shoulders i1 on the attaching tabs l1 in cooperationwith a rearwardly embossed central portion 3| on the rear wall iii ofthe front control unit. The rearwardly embossed portion 2| has a fiatwall portion 32 parallel to the wall it but offset rearwardly out of theplane thereof a distance corresponding to the thickness of theconventional spacer plate, and the, embossed por-- tion thus provides apad centrally of the shoulders l1 on the rear attaching tabs which isheld engaged with the front side of the base i i of the rear controlunit by the tabs l8 so that the two control units are held securelyattached together in coaxial relationship and properly axially spacedfrom one another,

The flat wall 32 of the embossed portion II is provided with asubstantially key-hole shaped opening 33. The small diameter end ll ofthis opening is coaxial with the bearing provided by the bushing 26 andof a size to receive an annularly grooved portion 35 of the operatingshaft 21 for the rear control unit to substantially lock the shaft tothe housing of the front control unit against substantially all axialmotion relative thereto. It is to be understood, of course, that thelocation of the annular groove 35 lengthwise of the shaft 21 is such asto hold the contactor of the rear control unit engaged with itscooperating collector ring and resistance strip under the desired degreeof spring tension, and that the rear wall It and particularly theoutwardly embossed center portion 32 thereof receives any rearwardthrust upon the shaft 21. Hence the rearwardly facing shoulder on theshaft, defined by the annular groove 35, and which overlies the portionsof the wall 32 surrounding the small diameter end 34 of the keyholeshaped opening, provides a thrust bearing on the shaft 21 to transmitrearward end thrust on the shaft to the housing of the front controlunit.

The larger end portion 31 of the key-hole shaped aperture 33 has adiameter sufficiently large to slidingly receive the ungrooved portionsof the operating shaft 21, and enables attachment of the assembled rearcontrol unit to the bottom wall I6 on the cup-like housing part 1 of thefront unit prior to assembly of the parts of the front control unit inthe housing 1. In other words, with the rear control unit 6 in acompletely assembled condition, and its operating shaft 21 extendingforwardly through a hole 29 in the insulating base II in which the shaftis loosely rotatably received, the cup-like housing part 1 for the frontunit is slipped on over the forward end of the shaft 21 with the shaftreceived in the enlarged portion 31 of the key-hole shaped opening, andmoved rearwardiy along the shaft to seat its centrally embossed portion2| against the base ll of the rear unit. With the parts in thisposition, the shaft 21 is drawn forwardly slightly to bring its groove25 into the plane of the flat wall 32 of the embossure, thereby allowingthe housing to be shifted laterally for engagement of the groovedportion 35 of the shaft in the small diameter end 34 of the key-holeshaped opening 33.

An end thrust bearing 40 is also provided for the tubular shaft 25 ofthe front control unit 5. This thrust bearing is formed as a metallicstamping having a flat body portion 4| received on and fixed to theinner end of the 'shaft 25 (as shown in Figure 5) rearwardly of butdirectly flatwise adjacent to the driver 23 so as to be normal to theaxis of the operating shaft. At diametrically opposite portions of itsperiphery the body is provided with lateral extensions bent to providelegs 42 projecting rearwardly toward the back wall I6 of the housing,and the extremities of the legs are bent in opposite directions toprovide feet or runners 43 flatwi'se engaged with the inner surface ofthe back wall l6.

Consequently, any rearward end thrust upon the shaft 25 is transmittedthrough the feet 43 of the thrust bearing 48 directly to the rear wallof the front housing which, therefore, receives any rearward end thrustimposed upon either of the operating shafts 25 or 21. Attention isdirected to the fact that in both instances the portions of the backwall [6 which receive the end thrust are adequately reinforced againstdeflection or deformation, In the case of the shaft 21 for the rearunit, it will be noted that the end thrust is transmitted directly tothe wall 32 of the outward embossure 3| which, of course, is backed upby the insulating base H of the rear control unit. In the case of thetubular operating shaft 25 for the front control unit it should beobserved that .the feet 43 of the thrust bearing 40 engage the rear walll6 of the front housing directly at its junction with the outwardembo'ssure 3|. Consequently, the more or less frusto-conical side wall45 of the embossure 3| receives such rearward end thrust and is placedin compression between the bearing feet 43 and the insulating basebehind it.

As indicated previously the thrust bearing 43 also serves as a rotationstop and for this purpose one of the feet 43 thereof has an extension 48thereon offset forwardly from the plane of the feet. This extensionprojects radially outwardly toward the side wall of the front housingfor cooperation with an indentation 49 in the junction with the centraloutward embossure ll thereon. The extremities of the legs 42" areslightly rounded to make turning of the tubular control shaft 25' assmooth and easy as possible.

In this embodiment of the invention also, a radial extension 48' on thebody 4| projects outwardly toward the side wall of the housing forcooperation with an indentation 49' in the side wall of the housing tolimit rotation of the shaft 25'. It will be noted that the extension 48,though offset rearwardly from the plane of the body 4|, is neverthelessspaced sumciently forwardly of the attaching tabs III as to eliminateany possibility of interference with rotation of the control shaft.

From the foregoing description taken together with the accompanyingdrawings, it will be readily apparent to those skilled in the art thatthe variable resistance control device of this invention achievessimplicity of construction and lower manufacturing cost through theelimination of parts previously considered essential, and achieves thisdesired simplicity without sacrificing ruggedness and high qualityconstruction.

What we claim as our invention is:

1. In combination: two electrical control units each having oppositefront and rear'walls in fixed spaced apart relationship, said unitsbeing fixed together in tandem relationship with the front wall of therear unit in juxtaposition to the rear wall of the front unit; a tubularoperating shaft for the front unit rotatably journalled in the frontwall of said front unit and projecting rearwardly into the interior ofthe front unit to have driving engagement therein with mechanism to beactuated; a second operating shaft rotatable inside said tubular shaftand projecting rearwardly through apertures in said juxtaposed walls ofthe two units into the interior of the rear unit to have drivingengagement therein with mechanism to be actuated; and means on each ofsaid operating shafts defining abutments overlying inner surfaces of therear wall of the front unit and cooperating with said rear wall thereofto support each shaft against rearward end thrust thereon.

2. The combination set forth in claim 1 further characterized by theprovision of an axially wall of the housing to limit rotation of thetubular shaft 25. Hence, it will be noted that the extension 48 providesa rotation stop spaced a sufficient distance forwardly from theattaching tabs I8 as to avoid any interference with rotation of theoperating shaft 25.

The dual resistance control device of Figures 6 and '7 is even morecompact than the device of Figures 1 to 5 inclusive. Consequently, thereis considerably less area on the rear wall l6 of the front control unithousing, between the tabs l8 and the rotation stop 49, for engagement bythe thrust bearing 40. Feet or runners such as used in the previousembodiment cannot be employed in this instance because they wouldcollide with the attaching tabs I8 and interfere with proper rotation ofthe operating shaft 25 for the front control unit.

A combined thrust bearing and rotation stop 40, therefore, is employedin this form of the invention. Instead of feet, the thrust bearing 40'has three circumferentially equi-spaced legs 42 extending rearwardlyfrom its body 4|, and the extremities of the legs have endwise abuttingengagement with the fiat inner surface of the adjacent rear wall l6directly alongside its rearwardly embossed central reinforcing portionon the rear wall of the front control unit engaging the front wall ofthe rear control unit to hold said units properly spaced apart.

3. The combination set forth in claim 2 further characterized by theprovision of shoulders on the rear control unit engaging exteriorsurfaces of the rear wall of the front unit at areas spaced radiallyoutwardly of said centrally embossed portion and cooperating therewithto hold the attached units properly spaced apart.

4. The combination set forth in claim 2 further characterized by thefact that the abutment defining means on the tubular shaft hasengagement with the inner surface of the rear wall of the housing forthe front unit at areas directly adjacent to its junction with saidrearwardly embossed central portion thereof.

5. The combination set forth in claim 2 wherein said outwardly embossedcentral portion on the rear wall of the front control unit has a flatwall portion normal to the axis of the operating shafts, and furthercharacterized by the provision of a key-hole shaped opening in said flatwall portion, and an angularly grooved portion on the operating shaftfor the rear control unit received in the small diameter end of thekeyhole 7 shaped opening to substantially lock the shaft of the rearcontrol unit to the rear wall of the housing for the front control unit.

6. In an electrical control device: a control unit; a housingfor saidcontrol unit including opposite front and rear walls in fixed spacedapart relationship; means for operating the control device including ashaft rotatably journalled in a bearing in the front wall of saidcontrol unit and extending rearwardly into the housing thereof andthrough an opening in the rear wall of said housing; said shaft havingan annular groove therein lying in the plane of that portion of thehousing rear wall through which the shaft projects and the rear wall ofthe housing having laterally adjacent, communicated apertures therein,one of which is coaxial with said bearing but smaller in diameter thanthe adjacent ungrooved portions of the shaft and in which the groovedportion of the shaft is received, whereby the shaft is substantiallylocked to the rear wall of the hous ing against axial motion relativethereto, the other aperture being large enough to accommodate the shaftfor endwise sliding motion therein.

7. The electrical control device set forth in claim 6 wherein saidlaterally adjacent communicated apertures are formed in a centralportion of the rear wall of the housing which is embossed axiallyrearwardly, out of theplane of said rear housing wall.

8. In an electrical control device: a. control unit having a housingincluding opposite front and back walls in fixed spaced apartrelationship: a stationary element inside said housing :secured to thefront wall thereof; a rotatable element inside the housing andcooperable with :said stationary element; a cup-like housing part:secured to said control unit with its bottom wall in juxtaposition tothe outer surface of said front wall of the control unit, and the sidewall of the housing part projecting forwardly from said front wall; anoperating shaft for said control unit loosely rotata-bly journalled inan aperture in said front wall of the control unit and havin its rearend portion inside said rear control unit and fixed to the rotatableelement therein to rotate the same, said operating shaft having anannular groove therein adjacent to said bottom wall of the housing part,and projecting through a hole therein coaxial with but smaller than saidaperture in the front wall of the control unit and in which the groovedportion of the shaft is received to substantially lock the shaft againstendwise motion relative to the control unit, said shaft projectingforwardly through the interior of the cup-like housing part beyond therim thereof, and said shaft receiving hole being enlarged laterally to adiameter at least as great as that of the ungrooved portion of theshaft, in which the shaft may be projected during assembly of thehousing part with the control unit.

9. The electrical control device set forth in claim 8 wherein saidcoaxial and enlarged holes are located in a central portion of saidbottom wall of the housing part which is embossed rearwardly out of theplane thereof and has engagement with the front wall of the control unithousing to hold the cup-like housing part spaced therefrom.

10. In an electrical control device: a housin having opposing spacedapart front and rear end walls; cooperating stationary and rotatableelsments inside the housing, the stationary element being carried by thefront wall of the housing between the front wall and the rotatableelement; an operating shaft rotatably journalled in said front wall andconnected to said rotatable element inside the housing to transmitrotation thereto; and a metallic stamping fixed to the operating shaftto rotate therewith, said stamping having a relatively flat body portionfixed to the shaft and substantially normal to its axis. and a number ofcircumferentially spaced legs extending rearwardly from the peripheralportions of the body and endwise abutting the rear wall of the housingto provide a thrust bearing for supporting the shaft against rearwardend thrust thereon.

11. The electrical control device set forth in claim 10. furthercharacterized by the provision of a central rearwardly embossedreinforcing portion on the rear wall of the housing having a flat wallportion parallel to the rear wall of the housing but spaced a distancerearwardly thereof, and a substantially frusto-conical neck joining saidflat wall portion with the rear wall of the housing; said legs engagingthe rear wall of the housing directly adjacent to said frusto-conicalneck.

12. In combination: two electrical control units each having acylindrical housing including opposite front and rear walls in fixed,spaced apart relationship and a side wall extending between the frontand rear walls, the housing for the rear unit being smaller in diameterthan that of the front unit; a central embossure on the rear wall of thefront control unit projecting axially rearwardly therefrom, the rim ofsaid embossure lying in a plane normal to the axis of the unit and nopart of the embossure or rear wall of the front unit extendingrearwardly beyond the rim of the embossure; the rear wall of the frontcontrol unit having circumferentially spaced slits located radially.outwardly of the rim of the embossure and substantially in line with theside wall of the rear unit; forwardly facing shoulders on the side wallof the rear control unit spaced ahead of the front wall of said rearcontrol unit a distance substantially equal to the extent the rim of theembossure lies rearwardly of the slitted portion of the rear wall ofthe'front control unit; and tabs on the side wall of the rear controlunit projecting forwardly through the slits in the rear wall of thefront control unit into the interior thereof and bent over against theinner surface of its rear wall to clamp said rear wall of the front unitagainst the forwardly facing shoulders on the rear control unit and atthe same time draw the rim of the ernbossure against the front wall ofthe rear control unit to thereby securely hold the control units infixed spaced apart relationship.

ARTHUR M. DAILY. LIERVIN B. ARISMAN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,779,601 Kebler Oct. 28, 1930 1,926,196 Da Costa Sept. 12,1933 2,484,667 Arisman et a1 Oct. 11, 1949

